1. Field of the Invention Art
The present invention relates generally to the potable and gray water systems on board commercial and general aviation aircraft and the capability to drain their potable water system in-flight.
2. Description of the Related Art
More and more airports are imposing stringent rules and regulations regarding the dumping of fluids on the tarmac area whether it is potable water, gray water, or more hazardous materials like hydraulic fluids, or engine oils. Potable water systems need to be drained for a variety of reasons such as general aircraft maintenance, sterilization, and cold weather storage. Typical water systems have provisions to drain potable water on the ground through a skin port. Draining the potable water system in-flight is one way to eliminate the need to dump the potable water on the tarmac. Discharging liquid in-flight presents two problems: first the liquid may freeze at the exit point; second, it may come in contact with the skin of the aircraft and form an ice block which is hazardous to people in the ground. Both of those problems are overcome with the use of a heated drain mast. Heated drain masts are currently used to drain gray water overboard in flight. Federal Food and Drug Administration rules require physical separation between the potable water system and the gray water system to prevent potable water contamination. Dual port heated drain masts currently allow the drainage of both the potable and gray water systems with the required separation.
Most business jets and commercial size aircraft are delivered from the original equipment manufacturer with at least one, and commonly two, single port drain masts. Retrofitting the aircraft with a dual port drain mast can be accomplished by replacing the single port drain mast with a dual port drain mast. To retrofit an aircraft that already has two single port drain masts, it is advantageous to replace the aft most drain mast such that drainage from the new dual port drain mast is less likely to form an ice block on the exterior of the aircraft or other exterior components such as antennas and inlet ducts fairings. However, on certain aircraft the aft most drain mast location may be above the lowest level of one or more of the potable water tanks and/or their interconnect lines, which prohibits sufficient gravity draining of the tanks.
Draining the potable water system can be accomplished through a single port drain mast dedicated to the potable water system. In some cases this drain mast may need to be installed above the lowest level of the potable water tank and/or portions of the potable water interconnect lines. In those cases, potable water cannot be sufficiently drained using gravity.